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#205224 - 02/06/12 03:43 PM Electrical systems in mobile structures.  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 783
Winchester, NH, US
Whose rules do you follow when installing electrical systems in mobile vehicles and trailers?

For example I was involved in a project that was a mobile control center for a remote robotic system. The trailer was setup to connect to an outside power source, with either a generator or building feed. I assume that when we were connected to a generator, we needed to bond the neutral to the ground, but when we were fed from an existing service, we could not double bond the neutral to the ground.

What are the rules for the portable X-ray or dentistry trailers?

How about the panel truck that has a small workshop in it with lights, air compressor, and convience outlets for small power tools?

How about the portable video studios for large public entertainment events like the Superbowl or award shows?


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#205225 - 02/06/12 04:48 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,142
Estero,Fl,usa
If you can't twist these things around to be RVs I am not sure where the code would apply.

You may get some clout on the mobile medical facilities through your health department rules.


Greg Fretwell

#205226 - 02/06/12 05:10 PM Re: Electrical systems in mobile structures. [Re: gfretwell]  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 783
Winchester, NH, US
So the NEC does not directly apply to mobile trailers, trucks, etc, that are not Recreational Vehicles.

OK, that makes sense.

Now, who's rules do apply?


#205227 - 02/06/12 05:54 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,142
Estero,Fl,usa
I think that with the possible exception of medical facilities, probably covered by the state health agencies, these are largely unregulated.


Greg Fretwell

#205229 - 02/06/12 07:59 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Larry...

The US Federal Government has jumped in and regulates them.

Manufactured homes are somewhere under HUD

Their site associated connection are regulated by the NEC/ States.

Because road-borne anythings cross state lines the Feds have long regulated them.

As a practical matter, the methods and fittings seen in manufactured housing are often identical to that of RVs.

Unlike stick-built homes, it would be most unusual for specific construction inspection for either manufactured housing or RVs.

-------

In either event, I'd run away before I ever got involved trying to correct wiring problems in manufactured housing. They're built to be built -- not repaired.



Tesla

#205231 - 02/06/12 08:29 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
HotLine1  Offline


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Joined: Apr 2002
Posts: 6,883
Brick, NJ USA
Larry:
Over the years, I worked (as EC) for a company that did 'first responder' type vehicles. A few of the larger rescue rigs had gensets & 'shore power' with 120/208 or 120/240, 3 phase QOB panels.

Doing the installs, repairs, retrofits, etc. we followed the 'plans' from an engineer. That was based on NEC, and trade practices. A manual, 4 pole transfer sw did the gen/shore power choice. Gen and shore were bonded to the truck frame. All the 120 was GFI.

Shore power was via a 100 amp (overkill) RS pin & sleeve.



John

#205232 - 02/06/12 08:50 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,142
Estero,Fl,usa
If this is not a mobile dwelling I do not see how HUD can regulate it and I am not sure the "first responder" vehicle is legally required to be inspected although I can see why the government's insurance carrier might want it.

I inspected a trailer IBM set up to display a small computer system but it was acting as the IBM Installation Planning Rep, not as an electrical inspector and this thing traveled all over the country. I never heard of any problems. It was set up to plug into a garden variety 50a RV post. (actually 2 for the full boat load) Internally there were 2 50a panels, one for the house loads and one for the computer system.
This had no "living" facilities (plumbing or sleeping area) so they dodged HUD. Actually, unless the rules have recently changed, RVs are not HUD regulated either.
My son in law had a trailer that was really a house on wheels but it was titled as an RV and was not HUD certified.

These guys
http://www.nationalcabinsales.com/ but they called themselves Stewart Lodges then.


Greg Fretwell

#205235 - 02/06/12 09:38 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,883
Brick, NJ USA
I neglected a few things. THe rigs were 'inspected' by the engineer, and a heck of a lot of firemen, EMTs & police.
I have no clue about any insurance inspections.

The 'shore power' receptacles were permitted and inspected.

As to Teslas comment regarding HUD, I believe he thinks the OP is talking mobile homes, which are HUD inspected. The 'manufactured' homes (prefab) that I have seen are inspected at the point of manufacture, by an 'in-plant' inspector that signs off on the finished product.

Sorry, if I mislead anyone.


John

#205237 - 02/06/12 09:54 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
WESTUPLACE  Offline
Member
Joined: Mar 2004
Posts: 251
Kingwood, TX USA
Do not bond the neutral and ground. If the on board generator has the neutral and ground bonded then use a transfer relay that switches the neutral. I wire many of these type units. I got into battles with EMS vehicle builders who would put a panel board on the vehicle and connect the neutral and grounds together. When the EMS operator would remove the shoreline cord, they would get a shock due to the grounded conductor being lifted before the hot. This would briefly cause the chassis to become hot. If the shore power was connected to an receptacle that the neutral and hot were reversed (or a 3 to 2wire adapter was used and there was a poor or no ground, the outside of the chassis will be hot. As long as the neutral is kept isolated at least the chassis will not become energized. This is also why many older camper trailers trip a gfci (and why there are a lot of campgrounds with rigged wiring) Campers also have a small panel board and most used the neutral bar for both the grounds and neutrals. GFCI's do not like that!! Robert


#205238 - 02/06/12 09:59 PM Re: Electrical systems in mobile structures. [Re: LarryC]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,883
Brick, NJ USA
Robert:
Thank you for the above. Reading back my comments, I neglected to be specific on having the neutral isolated from ground.


John

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